U.S. Pat. No. 4,508,842 discloses a highly active vanadium-containing catalyst system suitable for producing ethylene polymers comprising:
(A) a solid catalyst component consisting essentially of
(1) an inorganic carrier, as support for PA0 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA0 (3) a boron halide or alkylaluminum modifier, PA0 (B) an alkylaluminum cocatalyst, and PA0 (C) a halohydrocarbon polymerization promoter. PA0 (a) a vanadium chloride, PA0 (b) an alkylaluminum alkoxide, and PA0 (c) an inert inorganic support, PA0 (1) a solid, particulate, porous inorganic carrier, as support for PA0 (2) the reaction product of (a) a vanadium trihalide and (b) an electron donor, and PA0 (3) a boron halide or alkylaluminum modifier,
U.S. Pat. No. 4,232,140 also discloses a highly active vanadium-containing catalyst system for polymerizing ethylene, said catalyst system comprising:
(A) a solid catalyst component containing:
(B) an alkylaluminum cocatalyst, and
(C) a halogenated alkane.
The high yields obtained with this catalyst system is, according to the reference, dependent upon the use of a particular halogenated alkane, i.e., trichlorofluoromethane, as a polymerization promoter.
Japanese Public Disclosure No. 62-25112 (Application Ser. No. 60-163525) likewise discloses a vanadium-containing catalyst composition useful in the preparation of ethylene polymers. Such composition consists of:
(1) a solid catalyst component obtained by precipitating vanadium trihalide from an ether solution onto a silica and/or alumina carrier and then treating the product with an alkylaluminum,
(2) an alkylaluminum,
(3) an alkyl halide, and
(4) an alkoxy compound of silicon.
Unfortunately, the presence of the alkoxysilicon compound in such composition has been found to adversely affect polymer productivity.
Japanese patent publication 86/130313 (Japanese patent application Ser. No. 84/251743) likewise discloses vanadium-containing catalyst compositions useful in polymerizing olefins. Such compositions are obtained by mixing together a vanadium compound and an organoaluminum compound which has been previously modified with an ether, ester or ketone. The organoaluminum compound may be an alkylaluminum compound or an alkoxyaluminum compound.
According to this reference, polymerization activity is adversely affected if the vanadium compound is pre-reacted with the ether, ester or ketone.
Japanese Patent Publication 86/126111-A (Japanese patent application Ser. No. 84/248159) is yet another reference which discloses vanadium-containing catalyst compositions useful in polymerizing olefins. The catalyst compositions of this reference are prepared by combining (a) the reaction product of vanadium tetrachloride with an ether or ester with (b) an organoaluminum compound which has been modified with an ether, ester or ketone. The organoaluminum compound may be an alkylaluminum compound or an alkoxyaluminum compound.
According to this reference, polymerization activity is enhanced by the use of such catalyst. However, this activity enhancement appears to be peculiar to vanadium tetrachloride based catalysts.